You're welcome. I only discovered phone activation after calling to enquire if I could add a software subscription on to an ongoing annual subscription.
I've rechecked my FTMM3 and the first call is to resolve tags.tiqcdn.com and then connect on port 80. It then moves on to googleadservices, social media links etc. If I let them all through, but keep ABP and Ghostery enabled, I am met with a blank box titled 'In App Purchase'. Disabling the extensions gets me further as I notice that it is checking Ancestry and then iTunes for subscription options. Once this is complete, it gives me the information on my current subscription membership. Presumably your copy is hanging at the point where it is checking for available subscription options? Maybe mine works purely because I don't need a subscription? I usually remain logged into the MAS; I don’t know if that would make a difference regarding the iTunes check? To be honest though, I'm not sure it is worth you spending time to troubleshoot this.
In addition to the MAS FTMM3, I have FTM 2010 for Mac. Out of interest I tried installing it in Yosemite PB4. Prior to accepting an update, I noticed that the license agreement for FTM 2010 for Mac states that the software is published under license by Avenquest. In the 'About Family Tree Maker' box it states that the software was developed by Software MacKiev, the same as FTMM3. According to this article
http://www.bloomberg.com/apps/news?pid=conewsstory&sid=a..., Nova Development is a subsidiary of Avenquest. For anyone reading this and wondering what happened after the update, I can tell you that FTM 2010 failed to open. Each launch gives me the following 'Family Tree Maker cannot be opened because of a problem. Check with the developer to make sure Family Tree Maker works with this version of OS X.' The good news is that the MAS version of FTMM3 is working ok* with Yosemite PB4.
*appears to be the same as Mavericks; no new bugs encountered...